EW Physics at a SuperB Flavour Factory with Polarized Beam and status of some Flavour Physics with Taus J. Michael Roney University of Victoria III Prometeo.

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Presentation on theme: "EW Physics at a SuperB Flavour Factory with Polarized Beam and status of some Flavour Physics with Taus J. Michael Roney University of Victoria III Prometeo."— Presentation transcript:

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EW Physics at a SuperB Flavour Factory with Polarized Beam and status of some Flavour Physics with Taus J. Michael Roney University of Victoria III Prometeo Workshop IFIC 16 November 2010

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Polarised Beams provide an impressive Precision EW Programme at SuperB polarised beam provide measurement of sin 2 Θ w(eff) of using muon pairs of comparable precision to that obtained by SLD, except at 10.58GeV Similar measurement can be made with taus and charm Test neutral current universality at high precision Because it depends on gamma-Z interference it is sensitive to Z’ Measure NC Z-b-bbar vector coupling with higher precision and different systematic errors than determined at LEP with A FB b and at high precision 18 J.Michael Roney

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Comments on Beam Polarization Systematic Errors at SLC (thanks for discussions with Peter Rowson – SLD/SLD SLAC) 1) The left-right luminosity asymmetry must there be controlled to the level of the stat error (10 -6 ). At the SLC, able to monitor this asymmetry (using various beamline instruments) to a precision of ~ 0.5x 10 -4. One needs two orders of magnitude improvement here. 2) SLC needed to experimentally limit the level of accidental positron polarization - which was done at the SLC to the 7 x 10 -4 level. In principle, this too would have to be improved by two orders of magnitude, but in a storage ring perhaps this effect might be expected theoretically to be very much smaller and not an issue. 3) SLC able to completely ignore left-right asymmetric effects in the SLD detector efficiency at the SLC where ALR was ~10% (These effects that cause the response of the detector to a fermion at a given polar angle to differ from the response to an anti-fermion at the same polar angle). When effects at the part per million level are relevant, this issue would have to be re-examined. Perhaps this is still OK. 20 J.Michael Roney

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The L-R luminosity asymmetry is the most important and has to be controlled. This can likely be achieved with good luminosity monitoring using Bhabhas. Some thought needed to go into this. Comments on Beam Polarization Systematic Errors at SuperB 21 J.Michael Roney

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Similar approach for taus and electrons 22 J.Michael Roney Will give most precise NC universality measurements All error ellipses would be only slightly larger than red electron ellipse

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next two slides courtesy of Oscar Vives BOTTOM LINE: work concludes that A LR from BBbar events at the 4S giving access to the Z-b-bbar vector coupling is indeed sound and in fact very robust! INDEPENDENT of whether via Continuum or Resonance 25 J.Michael Roney

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At SuperB no QCD corrections At LEP QCD corrections were required – hadronization effects, hard gluons, etc We think it was done properly with correctly assessed systematic uncertainties, but… Real advantage at SuperB over a high energy machine, e.g. Z-factory, is that these corrections do not exist: we are coupling to pseudoscalars with no hadronization 30 J.Michael Roney

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Similar approach can be used for Charm Operate at a ccbar vector resonance above open charm threshold psi(3770) If we want to get charm in the same way, need to have polarization at lower energies with sufficient luminosity Alternatively, use 4S data and deal with hadronization 31 J.Michael Roney

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What if unpolarized beams? Can still access some information for e + e -    - via A FB but very difficult: Competition with A FB from QED box diagram Need to control real detector FB charge asymmetries: note that at LEP the smallest systematic error achieved on A FB was 0.0005, this would translate into an unacceptably large error on sin 2 ϑ eff W other errors arise, e.g. boost J.Michael Roney 32

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What if unpolarized beams? Can’t directly access Z-b coupling from A FB : Y(4s) decays to pseudoscalars, so no sensitivity Proposal to measure at Y(3S) via tau polarization where tau-pairs are produced in decay of Y(3S) (Bernabeu, Botella, Vives, Eur.Phys.J.C7:205-215,1999. ) In principle, very nice idea. In practice, need: to: Run at Y(3S) Need precise determination of continuum to Y(3S) production rate: so need equal amount of off-resonance data Then, deal with backgrounds &tc…. J.Michael Roney 33

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CKM Unitarity Triangle Physics beyond the SM signaled by breakdown of unitarity of CKM matrix J.Michael Roney 38 Area of Δ~CP violation Wolfenstein parameterisation defined to hold to all orders in  and rephasing invariant

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CKM experimental programme J.Michael Roney 39 Make as many precision measurements as possible that overconstrain the four CKM parameters (A, λ, ρ, η ) New Physics would be revealed in discrepancies between measurements Generally requires non-perturbative QCD input to convert measurements to a SM CKM interpretation

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Programme: Over constrain CKM with broad set of measurements J.Michael Roney 40 Quantity Sample Measurement(s) Although we probe the charged weak interaction, we need input from strong interaction calculations, which are difficult and often need data

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J.Michael Roney 52 B + →τ + ν τ Results this is not easily attributed to problem with f B because a 2.6 σ difference persists when considering: B Bd is the ‘bag parameter’ and is calculated on the lattice.

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Most precise CKM test is from the unitarity condition: From the 1 st row of the CKM matrix |V ub | is negligible in comparison to |Vud| ~1 and |V us | ~0.2 |V ud |=0.97425(22) is most precisely obtained from super-allowed nuclear beta decay |V us | is most precisely obtained from Kaon decays J.Michael Roney 53

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Summary and Prospects Flavour sector provides a means of probing physics beyond the SM at the precision frontier Polarised beams provide unique ability to determine both Z-lepton and Z-b couplings to highest precision The SM describes the flavour data, but there are seen a few ‘tensions’ in the flavour sector requiring attention Looking forward to new data from LHCb and in the future SuperB and SuperKEKB J.Michael Roney 61